This invention relates to static structures and more particularly to an improved cover or roofing structure for buildings.
Many commercial buildings, such as stores, theaters, and the like, are provided with a nearly flat roof. Because of the small slope to the roof, roofing shingles are not suitable as a roofing material since water can enter under the overlapping shingles. Typically, the roofing structure for a building of this type is built up from layers of tar paper, tar and stones to obtain a waterproof construction. However, considerable labor and expense is required to install a roof of this type. Furthermore, additional tar and stones periodically must be applied to the roof in order to maintain its waterproof integrity.
Another and less expensive type of roof construction for buildings having nearly flat roofs involves the use of sheets of a synthetic resinous material, such as sheets of a felt backed polyvinyl chloride. The sheets are unrolled across the roof with the edges of adjacent sheets overlapped. A waterproof mastic or adhesive is then applied to the overlapping edges to seal the edges together. This roof structure is relatively inexpensive to apply. However, the structure has a limited durability, particularly at the joints between adjacent sheets of the material. During heavy rains, the joints will be under water and subject to at least a small pressure head. As the joints age, they will tend to leak due to a breakdown of the mastic or adhesive. Another problem occurs with sweating. Any moisture absorbed by the building prior to application of the roof tends to collect between the vinyl roofing material and the building. This moisture can adversely affect the lifetime of the roofing material and of the building roof itself, particularly when the roof is formed from wood.